This invention is for a process and an apparatus for manufacturing and for the subsequent handling of printed circuits, and particularly for manufacturing small numbers of single printed-circuits.
At present, the etching of prepared printed-circuit boards takes place in etching machines, in trays, in sinks, and in vessels. Particularly for laboratory use, where a printed circuit infrequently is made, it is uneconomical to use an etching machine. Not only is the investment relatively high for an etching machine, but the etchant must be kept at a constant temperature in order to avoid crystallization of the etchant solution. Thus, for laboratories where only a few printed circuits are produced, the use of an etching machine does not make much sense.
A problem with etching printed-circuits in trays lies in the fact that such trays are used only for the etching process itself. The etchant has to be prepared elsewhere and heated, and then poured into the tray. Thus, a certain amount of spillage or staining is usually unavoidable. In addition, considerable evaporation takes place because of the relatively large surface area; the disadvantage of this is that these fumes are highly corrosive. In addition to the fumes, another problem with trays lies in the need to keep the etchant at a certain temperature, which is difficult to do with open trays. Care must also be taken to avoid gas blisters on the circuit board, which result from the waste deposits of the etchant. After the etching process is concluded, the etchant must be removed from the tray to a container since the tray is unsuited for storing the etchant for a long period of time. Thus, there is again danger of spillage or staining. A further disadvantage of etching printed circuits in trays is that a relatively large and uneconomical amount of etchant is required in relation to the size of the printed circuit board itself. Thus, the relationship of the etchant volume to the size of the board is much too high.
Generally, the same problems that occur when etching in trays arise when etching printed circuits in sinks. Although the surface area in sinks is usually smaller in relation to the etchant volume than in trays, and it is sometimes possible to seal a sink with a tight cover, thus using the sink as a storage area, nevertheless escaping fumes cannot be avoided. and it is difficult to heat the etchant in the sink from the outside. The heating is sometimes accomplished by means of a specially installed heating system in the sink or by means of immersion-heaters. In both cases, however, special safety precautions must be followed. Since the size of the sink is determined by the size of the largest printed circuit to be etched, the relationship of the etchant volume to the size of the printed circuit board is very great. This requires a relatively long heating period. Since sinks of this kind are usually high and narrow, the printed circuits must be fastened by means of special clamps before they can be immersed into the etchant. As in the case of the other known etching apparatuses, a further drawback of this kind of sink is that the process of the etching process cannot be observed without removing the board from the etchant. Thus, it is not possible to influence the etching process in individual cases by shortening the process on areas that are already fully etched or ever-etched, or lengthening the process on areas not sufficiently etched.
In summary, the aforementioned known methods and apparatuses which are now available to meet the needs of development laboratories, research institutes, schools and hobbyists are too costly, complicated, unhygienic and unwieldy. This is also true when treating circuit boards by developing a photo-resist coating, and when further handling a printed circuit by gold-plating, silver-plating or zinc-plating.
Therefore, there is a need for a process and an apparatus with which printed circuits can be developed, etched, tin-plated, silver-plated and gold-plated in a simple, economical and hygienic manner.